1. Field of the Invention
The invention relates to a shut-off instrument for a flow medium.
2. Description of the Related Art
From the document DE 1 093 634 a shut-off valve is known with a shutting-off element comprising a carrier and a casing made of elastic material. The shutting-off element encased with elastic material is in the form of a hollow cylinder that is closed on one side in the form of a spherical indentation, which cylinder is provided on its outer surface with the casing made of elastic material, and is adjustable from a position of blocking the flow channel of a valve housing into a position of opening the flow channel. This performed by means of a threaded stem mounted rotatably and sealingly in a neck extension of the valve housing, the thread of which engages with an internal thread in the shutting-off element. The elastic casing forms, together with diametrically opposite guide tracks and guide grooves receiving the latter in the housing in a plane perpendicular to the flow direction, a linear guide for the positioning of the shutting-off element so that the latter cannot rotate and is supported against the pressure of the medium. The stem bearing in the neck extension makes a pendulum movement of the adjusting stem possible by means of an elastic bearing and sealing element to obtain a sealed bearing on sealing surfaces surrounding the flow channel.
From a further document DE 527 748 a sealing device is known for a sealing body of a stopcock or valve or slide valve, in which the sealing body comprises a hollow cylindrical main body closed at one end and, which is provided on the cylindrical outer surface with a casing made of elastic material for sealing arrangement in a housing shaping of a valve housing forming the flow channel. The adjustment of the sealing body is performed by an adjusting stem in a vertical direction determined by the flow direction in the flow channel, whereby the sealing body is provided with diametrically opposite guide wings which engage in linear guide grooves of a neck extension, and thus there is no risk of twisting and guiding. In order to avoid deformations to the hollow cylindrical sealing body caused by the pressure of the medium, bores traversing the casing and walls of the sealing element are provided which equalize the pressure.
A method for producing a shut-off instrument and a shut-off element are known from DE 19 16 347 A1, which comprises a one piece element housing with a housing part forming a flow channel and a housing extension which forms a slide valve chamber for a wedge-type valve and a stem bushing with sealing arrangement and is joined in one piece to the housing part, for completely mounting a shut-off element designed with the slide valve stem-movable as a wedge-type valve, which is guided in the element housing in such a way that it cannot be twisted. The design relates to a so-called hard sealing slide valve instrument and sealing elements forming sealing surfaces opposite the flow channel are arranged; to which diametrically opposed sealing faces on the wedge-type valve are allocated. In order to manufacture a one piece housing for a shut-off instrument of this kind an expensive mould structure and moulding procedure is necessary, in order to position the premanufactured wedge-type valve into a mould core and position it with the latter in a casting mould.
Furthermore, a shut-off instrument with a housing that is essentially in one piece is also known from DE 33 02 979 A1, which is provided with a lateral assembly opening for inserting the shut-off instrument and the bearing arrangement, and which can be sealed with a housing lid. In order to achieve the required tightness, in particular at higher nominal pressures, it is necessary to shape the housing and the housing lid on the sealing surfaces and design the securing of the housing lid in a particular way.